In recent years, game units and simulators equipped with on-board virtual image generation apparatuss which make it possible for movable objects (objects) which move through three-dimensional space to combat each other have been developed. Such virtual image generation apparatuss are usually equipped with a virtual image generation apparatus main unit that houses a computer unit for executing stored programs, an input device for sending control signals to the computer unit to instruct it to move objects displayed on the screen within the virtual image, a display for displaying the virtual images generated by the computer unit according to the program sequence, and a sound device for generating sounds according to the program sequence.
Examples of devices with the architecture described above include driving game unit with a car race theme, in which cars compete with enemy cars on a circuit, and simulators which re-create the experience of piloting a helicopter or airplane. In this type of device, highly realistic simulation of car or helicopter movement is extremely important. For example, in a driving game like that depicted in FIG. 8A, input devices which resemble an actual car steering wheel, accelerator pedal, and brake pedal are used. In a helicopter or other simulator input device are processed by the CPU (central processing unit) of the computer unit. The computer unit repeatedly performs calculations to assign relative position within the virtual space to the objects, including data for enemy object motion when enemy objects are also present
As players become more skilled at playing games, it has become necessary to go beyond conventional motion and develop movable objects such as player-controlled robots, humans, and the like. Particularly in the field of game devices, games are being developed in which objects not only move in two dimensions over a terrain created in virtual space (hereinafter termed "virtual terrain"), but also jump up from a virtual terrain in order to jump over another character or engage in fights in midair.
However, input devices for conventional virtual image generation apparatuss, while suitable for controlling two-dimensional motion of objects through a virtual space, are not adapted to controlling three-dimensional motion such as jumping. For example, in the driving games mentioned earlier, the steering wheel (which is the principal means of control) controls the movable object in the sideways direction (as viewed from the player's visual point), while the accelerator and brake pedals control motion in the forward direction; there is no way to control motion of the movable object in the vertical direction. Similarly, in simulators, a single control lever is used to control all motion of the movable object in three directions, the forward direction, sideways direction, and vertical direction.
In combat-style game units, the game unit must afford control sufficient to permit agile motion in order to avoid an enemy attack. In such cases, a special control button or control lever to control jumping can be provided, but this makes operation complicated and does not allow the action to be transmitted to the game unit with the same sense of speed that the player desires. In addition, excessively feature-laden input devices entail higher costs.
By way of improving control a video game unit which affords simple game control using two control levers is taught in Japanese Laid-Open Patent Application 6-277363. In this example of the prior art, thrust vectors are assigned according to the control lever inclination of each of the two control levers, and the two vectors are synthesized to produce complex actions.
However, in this example of the prior art, it is difficult to move the object rapidly in the desired direction through synthesis of the two vectors, and it is not possible to move the object freely to a desired position in three-dimensional space.
In order to solve this problem, it is an object of the present invention to provide a virtual image generation method and device which allow a movable object to be moved freely and without input error in three dimensions within a virtual space, and to a device therefor.